The present invention relates to medical monitoring devices and, in particular, it relates to a monitor for the detection of disorders of nocturnal skeletal muscle activity.
It is known that nocturnal skeletal muscle activity disorders are a common medical problem. Two such syndromes of this nature are bruxism (nocturnal teeth grinding) and Periodic Leg Movement Syndrome (PLMS).
Surveys show that over 5% of the adult population suffer from bruxism. In this condition, ongoing involuntary grinding of the teeth damages healthy enamel on the chewing surfaces of the teeth (possibly even causing stress fractures), and may cause damage to the tempero-mandibular joint. As such, Bruxism is a far more destructive process than is dental caries. However, only a minority of patients suffering from bruxism are aware of their condition. Usually, the patient is completely unaware of this disorder, and does not seek medical or dental attention until irreversible damage to their dentition has occurred necessitating extensive restorative treatment or tooth extraction. xe2x80x9cClenchingxe2x80x9d is a common variation of bruxism, and involves the non-purposeful closing of teeth in the chewing position. Both bruxism and clenching can occur during the day, but in most cases occur at night during sleep.
Periodic Leg Movement Syndrome (PLMS) is a common sensorimotor sleep disorder in which repeated involuntary, highly regular, jerky movements occur periodically, every 20 to 40 seconds, in one or both legs during sleep. PLMS may occur as an isolated phenomenon, but more often is associated with other sleep disorders such as Restless Leg Syndrome (RLS), narcolepsy, or sleep apnea. Surveys show that about 1% of the population over 40 years of age have either PLMS or RLS, and that the prevalence of the disorder increases with age. PLMS may also be associated with systemic diseases such as iron deficiency anemia, kidney failure, diabetes, rheumatoid arthritis, and peripheral neuropathy. PLMS and RLS may lead to severe sleep disruption and excessive daytime somnolence. As such, the patient may easily fall asleep during working hours, such as when the patient is driving a car or a truck
Definitive diagnosis of bruxism can be achieved by recording jaw muscle electromyographic (EMG) signals during sleep. So too, PLMS is best diagnosed by monitoring the EMG activity of the Tibialis Anterior (calf) muscle while the patient is sleeping. Both such EMG studies are often part of an in-lab, full night, formal sleep study. In such a study, the patient is required to sleep for a whole night in a controlled environment (a xe2x80x9csleep laboratoryxe2x80x9d) while connected to multiple monitoring devices, which continuously measure such physiological parameters as respiratory effort, nasal and oral airflow, brain electrical activity (EEG), Tibialis Anterior or jaw muscle EMG activity, heart rate and rhythm (ECG), and blood oxygen saturation. These parameters are recorded on paper or stored in a memory bank for later analysis. A trained sleep technician is required to oversee the study so as to ensure that all parameters are recorded properly. The data is then analyzed, either manually or by specialized software, to produce a xe2x80x9chypnogramxe2x80x9d which describes the nature of the patients sleep. Indices in the hypnogram, such as a xe2x80x9cbruxism indexxe2x80x9d and a xe2x80x9cleg movement indexxe2x80x9d, are then used, by a sleep specialist, to diagnose the patients pathology, and its severity.
Bruxism is initially treated with an xe2x80x9cocclusal splintxe2x80x9d bite guard, or by biofeedback techniques, however ongoing monitoring of the efficacy of treatment is necessary so as to determine if and when more aggressive medical or dental intervention is required. PLMS is managed with medications such as benzodiazepines, anti-dopaminergic agents, or opioids. Multiple trials of therapy may be necessary before the optimal drug and dosage is found, and a medication that is initially effective may lose its efficacy with repeated use. Thus PLMS, too, requires ongoing monitoring of the efficacy of treatment.
The formal sleep study as a means of diagnosing and following-up patients with sleep-related problems, however, suffers from several deficiencies and limitations:
1. The study requires the use of multiple medical monitoring devices and the continuous presence of a trained technician. It is thus labor intensive to perform, and requires the use of multiple, expensive, resources. As such, sleep laboratories themselves are a limited resource, each containing only a limited number of beds. This is particularly problematic as studies are often conducted on xe2x80x9csuspiciousxe2x80x9d patients, in whom the outcome is frequently negative. In such patients, for whom there was no need for the study at all, a limited screening study may have been sufficient to exclude sleep pathology. In addition, the study price often prohibits repeating studies on a regular basis for purposes of patient follow-up, and prohibits performing multiple studies for the screening of large populations.
2. The patient is asked to sleep in an unnatural sleep environment, which may itself affect his sleep patterns.
3. The patient is inconvenienced by having to be in a hospital setting for a night.
4. There is no patient privacy.
In order to overcome some of these drawbacks, the performance of home studies by means of ambulatory systems has become popular. These studies utilize miniature ambulatory recorders, and are sometimes limited to a relatively small number of information recording channels. The patient is prepared for the study at the sleep lab, and returns home with all sensors appropriately attached. Alternatively, a technician may come to the patient""s home, or the patient may attach the sensors by himself after receiving appropriate instruction from a technician. The study is then conducted in the patient""s home, as he sleeps in his own bed, and the recorded data stored in a memory device. In the morning the recorder and memory device are returned to the sleep lab for data downloading to an analysis station. Some of these ambulatory systems can correct for some data recording problems, by adjusting the gain or filtering during data recording or when post-processing the data. Alternatively, the study can be monitored from the sleep lab via a modem.
Although ambulatory sleep-monitoring systems are much more convenient to the patient, and considerably less expensive than formal, in-lab, sleep studies, all current ambulatory sleep-monitoring systems suffer from several deficiencies:
1. Performance of the study still requires the participation of a trained technician (for the purposes of either attaching the monitoring device or instructing the patient how to do so) and the participation of a formal sleep laboratory (for the purposes of downloading and analyzing the test results, and maintaining the equipment necessary for the performance of the test). Such tests are thus still labor and resource intensive.
2. As analysis of the recorded data is performed off-line in the sleep laboratory, the ambulatory monitoring device must be able to store all registered data in a suitable memory storage device, until such data can be downloaded. Alternatively, if the data is relayed to the sleep laboratory in real time, a modem and telephone line are necessary. Current ambulatory devices are therefore relatively complex and expensive to manufacture. As such, ambulatory studies are still too expensive to perform on a regular basis (currently approximately $500 per study), thus precluding their widespread use as a screening tool or for purposes of frequent patient follow-up. In addition, the cost of such studies does not justify their use on xe2x80x9cdifficultxe2x80x9d patients, such as mental health patients or small children, in whom the likelihood of technical failure of the study is high.
There is therefore a need for a nocturnal skeletal muscle activity disorder screening system that is suitable for widespread use for patient screening and follow-up. Such a system should be sufficiently simple to implement as to allow patients to perform the study at home, without the need for assistance from a trained technician. In addition, such a system should provide the patient with an easily understandable result at the end of the study, without the need for data processing at a sleep laboratory, and without the need for interpretation of the result by a physician or technician. Finally, such a system should be sufficiently inexpensive as to make multiple and frequent studies, for purposes of monitoring and follow-up, practical to finance.
The present invention is an ambulatory nocturnal muscle activity monitoring system. The invention integrates a minimal data-collection and analysis system into a disposable, single use device that achieves data-collection and analysis in real time, and outputs the study result in an easily understood format immediately following the study.
The entire system is incorporated into a single small, flexible, plastic unit which can be easily positioned, or placed, on the muscle group under study. The system is powered by a lithium, or similar, battery, which is irreversibly activated by means of the patient pulling on a tab. Once activated, electrodes input myoelectric data describing the pattern of muscle activity into a micro-processor, via an analog to digital converter. A flashing LED display indicates to the user that the device is functioning properly. A software module detects specific patterns of electromyographic activity and, together with real-time clock information, the presence of episodes of abnormal muscle activity is documented. After a predefined period of time, non volatile output flags (in the form of miniature electro-chemical cells, or heat sensitive colored dots) are set by the software, each output flag describing a specific study outcome. Once activated, the output flags undergo a permanent color change. As such, they produce an easily-read hard copy of the study results, informing the user whether significant abnormal muscle activity was detected and whether a physician need be consulted. Hereinafter, output flags which undergo a permanent change in color when activated by heat are referred to as xe2x80x9cheat sensitive permanent color display elementsxe2x80x9d, and output flags which undergo a permanent change in color when activated by an electrochemical process are referred to as xe2x80x9celectro-chemical permanent color display elementsxe2x80x9d.
The integration, onto an EMG sensor, of a muscle activity monitoring system which is capable of analyzing EMG data in real time and generating an immediate report thereof, is unique to the current invention. By xe2x80x9creal timexe2x80x9d is meant that the sensing of muscle activity and the processing of such sensed EMG data occur during the same time interval, or within a few seconds of each other, rather than the processing occurring after all muscle activity sensing has been completed.
As data is analyzed in real time, the need for a large memory storage unit to store data for later analysis, and the need for complex downloading hardware, are obviated. This feature allows the entire system to be manufactured in a small and inexpensive format, and provides the user with the result of the study immediately upon conclusion of the study, without the need for data processing and analysis by medical professionals at a sleep laboratory. Furthermore, as the power source, processor, and display mechanism of the device are all integrated with the EMG probe (or sensor) into a single small unit (without the need for cables or wires connecting these components to each other), and as an easily-seen flashing light confirms for the user that placement and operation of the device are correct, the device is simple and straightforward to use. The device can thus be operated without supervision by trained medical professionals. Accordingly, the cost per study is sufficiently low as to justify performing studies frequently for screening purposes (whenever there is even a slight chance of true pathology being present) or for regular patient follow-up. As there are no cables or wires connecting the EMG sensor with the rest of the device, the possibility that the sensor might be pulled off of the users body, due to the cable becoming entangled while the user is asleep, is obviated.
According to the teachings of the present invention there is provided a muscle activity monitoring system, including a muscle activity sensor, for sensing muscle activity at a location on a body; a processor, for analyzing the sensed muscle activity to determine the presence of a pattern of muscle activity, and for correlating the pattern of muscle activity with a diagnosis; a display, for displaying the diagnosis; a power source, for powering the muscle activity sensor, the processor, and the display; and a housing, for housing the processor, the display, and the power source, on the muscle activity sensor, the housing being placeable at the location on the body. There is also provided a muscle activity monitoring method, including the steps of placing a housing at a location on a body; sensing muscle activity at the housing during a time interval; processing the sensed muscle activity to detect a pattern of muscle activity, the processing occurring during the time interval; correlating the pattern of muscle activity with a diagnosis, the correlating occurring during the time interval; and displaying the diagnosis on the housing. There is also provided an electrochemical display system, including a cathode; an anode, and a layer of electro-conductive material covering at least part of the anode, the layer being operative to undergo an electrochemical process when electric current flows from the anode to the cathode, and wherein the electrochemical process eventuates in a change in a perceived color of the anode. There is further provided a method of irreversible display, including providing a cathode and an anode, the anode being at least partially covered by an electro-conductive material; inducing a flow of electrical current between the cathode and the anode, thereby effecting an electrochemical process in the electro-conductive material, and thereby causing a change in a perceived color of the anode.